Phase formation and properties of the BaO–B2O3–SiO2 and –Al2O3 ceramics prepared via an aqueous suspension route

• Published in: Journal of alloys and compounds 2012-09, Vol.536, p.73-79
• Main Authors: Chen, Song, Zhu, Degui
• Format: Article
• Language: English
• Subjects: BaO–B2O3 composition; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Dielectric properties; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Materials science; Mineral phase; Other materials; Permittivity (dielectric function); Physics; Sintering; Solid-liquid transitions; Specific materials; Specific phase transitions; Thermal expansion; thermomechanical effects and density; Thermal properties; Thermal properties of condensed matter; Thermal properties of crystalline solids
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.05.013

► Barium silicates and hexacelsian ceramics are prepared at the sintering temperature of 850–940oC. ► The BaO–B2O3 compositions can availably decrease the sintering temperature the barium silicate and hexacelsian ceramics. ► The presence of barium silicates and SiO2 crystal in the ceramics can urge a higher CTE (11–17ppmoC−1). ► The formation of a hexacelsian phase can achieve a low permittivity and loss (permittivity: 7.1–7.4; loss: 5–7×10−4). The low-temperature sintering ceramics based on the eutectic systems BaO–B2O3–SiO2 and –Al2O3 are fabricated by an aqueous suspension process at a sintering temperature of 900–940oC. Sintering mechanism and physical properties, e.g., dielectric and thermal properties, of the low-temperature sintering ceramics have been investigated and discussed in detail in terms of their mineral phase compositions. The results indicate that the barium borate compounds with low melting characteristics can be easily obtained by the chemical combination of Ba(OH)2·8H2O and an aqueous solution of H3BO3. In turn, the presence of the BaO–B2O3 composition in the low-temperature sintering ceramics can supply a liquid phase sintering aid for the mineral phase formation and the achievement of densification sintering. The addition of a SiO2 component to the BaO–B2O3 composition can cause the emergence of barium silicate phases and consequently achieves high coefficients of thermal expansion (11–17ppmoC−1), whereas the introduction of an Al2O3 component to the BaO–B2O3–SiO2 composition can result in the formation of a hexacelsian phase, which can achieve a low permittivity and loss (permittivity: 7.1–7.4; loss: 5–7×10−4). The work may be referenced for the fabrication of LTCC materials with tailored physical properties.